Memory device with a multiplexed command/address bus

ABSTRACT

A memory device includes a first plurality of volatile memories, a non-volatile memory, and a controller coupled to the non-volatile memory and including a first controller output. The memory device further includes a registering clock driver (RCD) including a first RCD output, and a first multiplexer including a first mux input coupled to the first RCD output, a second mux input coupled to the first controller output, and a first mux output coupled to the first plurality of volatile memories. The first multiplexer can be configured to provide command/address signals from one of the RCD and the controller to the first plurality of volatile memories.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.17/143,120, filed Jan. 6, 2021; which is a continuation of U.S.application Ser. No. 16/016,111, filed Jun. 22, 2018, now U.S. Pat. No.10,930,632; which is a continuation of U.S. application Ser. No.15/656,895, filed Jul. 21, 2017, now U.S. Pat. No. 10,147,712; each ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to memory devices, and moreparticularly relates to memory devices with multiplexed command/addressbusses.

BACKGROUND

Memory devices may be provided as modules with standard physical formatsand electrical characteristics to facilitate easier installation anddeployment across multiple systems. One such module is a dual in-linememory module (DIMM), which is frequently used to provide volatilememory such as DRAM to computing systems. Although DRAM can be fast, andtherefore well-suited to use as the main memory of computing systems, itis a volatile memory format and thus requires the continuous applicationof power to maintain the data stored therein. To address thislimitation, other modules can provide both volatile memory (for use asthe main memory of a system) and non-volatile memory (for backing up thevolatile memory in case of power loss) in a single module. One suchmodule is a non-volatile dual in-line memory module (NVDIMM).

NVDIMMs require more complex circuitry than is provided on a DIMM, inorder to handle the additional tasks an NVDIMM may be called upon toperform (e.g., power loss detection, backup and restore operations,etc.). The additional circuitry can make the design of an NVDIMM morechallenging, especially as the capacity (and therefore the number ofmemory chips) of the modules increases and the electricalcharacteristics to which the module must conform to meet the demands ofa standard format grow ever more stringent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a volatile memory module.

FIG. 2 is a schematic diagram of a non-volatile memory module.

FIG. 3 is a schematic diagram of a memory device in accordance with anembodiment of the present technology.

FIG. 4 is a schematic diagram of a memory device in accordance with anembodiment of the present technology.

FIG. 5 is a schematic diagram of a memory device in accordance with anembodiment of the present technology.

FIG. 6 is a schematic diagram of a memory device in accordance with anembodiment of the present technology.

FIG. 7 is a schematic diagram of a memory device in accordance with anembodiment of the present technology.

FIG. 8 is a flow chart illustrating a method of operating a memorydevice in accordance with an embodiment of the present technology.

DETAILED DESCRIPTION

In the following description, numerous specific details are discussed toprovide a thorough and enabling description for embodiments of thepresent technology. One skilled in the relevant art, however, willrecognize that the disclosure can be practiced without one or more ofthe specific details. In other instances, well-known structures oroperations often associated with semiconductor devices are not shown, orare not described in detail, to avoid obscuring other aspects of thetechnology. In general, it should be understood that various otherdevices, systems, and methods in addition to those specific embodimentsdisclosed herein may be within the scope of the present technology.

FIG. 1 schematically illustrates a DIMM 100 including a plurality ofDRAM memories 120 (e.g., memory dies, memory chips, memory packages orthe like). The DIMM 100 includes an edge connector 102 along an edge ofa substrate 101 (e.g., a printed circuit board (PCB) or the like) of theDIMM 100 for connecting a data bus 104 and a command/address bus 106(illustrated in bold lines) to a host device. The data bus 104 connectsthe DRAM memories 120 to the edge connector 102 and receives datasignals from and transmits data signals to a connected host duringmemory access operations (e.g., reads and writes). The DIMM 100 furtherincludes a registering clock driver (RCD) 110 that receivescommand/address signals from the command/address bus 106 and generatesmemory command/address signals for the DRAM memories 120. The RCD 110can present a predictable electrical load (e.g., for matching impedance,reactance, capacitance, etc.) to the host device and can re-drive memorycommand/address signals to the DRAM memories 120, which helps enablehigher densities and increase signal integrity. The RCD 110 may alsobuffer the command/address signals provided by the host, and thentransmit the buffered signals as memory command/address signals to theDRAM memories 120.

An NVDIMM can be configured similarly to the DIMM 100, with the additionof non-volatile memory and supporting circuitry and devices. One suchNVDIMM is illustrated schematically in FIG. 2. NVDIMM 200 includes botha plurality of DRAM memories 220 and a non-volatile memory (e.g., FLASHmemory 230). The NVDIMM 200 includes an edge connector 202 along an edgeof a substrate 201 (e.g., a PCB or the like) of the NVDIMM 200 forconnecting a data bus 204 and a command/address bus 206 (illustrated inbold lines) to a host device. The data bus 204 connects the DRAMmemories 220 to the edge connector 202 and receives data signals fromand transmits data signals to a connected host during memory accessoperations (e.g., reads and writes). The NVDIMM 200 further includes aregistering clock driver (RCD) 210 that receives command/address signalsfrom the command/address bus 206 and generates memory command/addresssignals for the DRAM memories 220.

The NVDIMM 200 further includes a controller 232 for controlling theFLASH memory 230 and performing memory management operations, such aspower loss detection, backup from the DRAM memories 220 to thenon-volatile memory 230, and restore from the FLASH memory 230 to theDRAM memories 220. The controller 232 may include a connection to theedge connector 202 (not shown) to facilitate detection of a power lossevent (e.g., by monitoring a voltage of a power supply pin, or via adedicated pin for sending commands from a connected host to thecontroller 232).

The controller 232 is connected to the FLASH memory 230 by anon-volatile bus 234 and to the DRAM memories 220 by the data bus 204.In this regard, the data bus 204 may include a number of datamultiplexers 208 to facilitate connecting the DRAM memories 220 to boththe edge connector 202 (e.g., for receiving data signals from andtransmitting data signals to a connected host) and to the controller 232(e.g., for reading data signals from the DRAM memories 220 during abackup operation and transmitting data signals to the DRAM memories 220during a restore operation). For example, in an embodiment in which eachof nine DRAM memories 220 have eight I/O terminals, the data bus 204 caninclude eight bus lines connecting each DRAM memory 220 to thecorresponding data multiplexer 208, eight bus lines connecting each datamultiplexer 208 to the edge connector 202, and eight bus linesconnecting each data multiplexer 208 to the controller 232 (e.g., whichcould be provided with 72 I/O terminals). In another embodiment, amemory module similar to NVDIMM 200 could include a further nine DRAMmemories 220 on a back side thereof (for 18 total DRAM memories 220,each having four I/O terminals). In such an embodiment, the data bus 204could include four bus lines connecting each of the eighteen DRAMmemories 220 to a corresponding one of eighteen data multiplexers 208,four bus lines connecting each data multiplexer 208 to the edgeconnector 202, and four bus lines connecting each data multiplexer 208to the controller 232 (e.g., which could be provided with 72 I/Oterminals).

The controller 232 is further connected to the RCD 210, in order toprovide command/address signals to the DRAM memories 220 during backupand restore operations. In this regard, the controller can include adriver 233 for sending command/address signals to the RCD 210, through acommand/address multiplexer 236 configured to connect the RCD 210 toboth the edge connector 202 and the driver 233 of the controller 232.Because the command/address multiplexer 236 of NVDIMM 200 is disposedbetween the RCD 210 and the edge connector 202 (and thus RCD is notdirectly connected to edge connector 202 by the command/address bus206), it can be challenging to ensure that RCD 210 presents apredictable electrical load (e.g., for matching impedance, reactance,capacitance, etc.) to a connected host device.

To facilitate the interchangeability of memory modules conforming to thesame standard, it is desirable to provide such modules with the samephysical interface (e.g., edge connector design, minimum and maximumphysical dimensions, etc.) and electrical interface (e.g., pin layout,circuit impedance, current draw, operating voltage, etc.). One challengeassociated with providing non-volatile memory on an NVDIMM, which isdesigned to the same physical and electrical characteristics of a DIMM,is the challenge of providing a predictable electrical impedance on thecommand/address bus while accommodating connectivity both to a hostdevice and to an onboard controller. In this regard, matching theimpedance of the command/address bus 206 at the edge connector 202 whena command/address multiplexer 236 is provided between the edge connector202 and the RCD 210 presents a particular challenge, especially as thememory capacity of a NVDIMM module is increased (e.g., by adding moreand/or larger DRAM memories).

Accordingly, several embodiments of data storage devices and computingsystems in accordance with the present technology can provide memorymodules with a multiplexed command/address bus that overcomes thelimitations of conventional memory modules. Several embodiments of thepresent technology are directed to a memory device comprising a firstplurality of volatile memories and a non-volatile memory. The memorydevice further comprises a controller coupled to the non-volatile memoryand including a first controller output, and a registering clock driver(RCD) including a first RCD output, and a first multiplexer. The firstmultiplexer includes a first mux input coupled to the first RCD output,a second mux input coupled to the first controller output, and a firstmux output coupled to the first plurality of volatile memories.

FIG. 3 is a schematic diagram of a memory device in accordance with anembodiment of the present technology. The memory device 300 may be anNVDIMM, or may have an alternative module format. The memory device 300includes a plurality of volatile memories 320 (e.g., DRAM memories) anda non-volatile memory 330 (e.g., NAND memory). The memory device 300includes an external connector (e.g., edge connector 302) for connectinga data bus 304 and a command/address bus 306 (illustrated in bold lines)to a host device. The data bus 304 connects the volatile memories 320 tothe edge connector 302 and receives data signals from and transmits datasignals to a connected host during memory access operations (e.g., readsand writes). The memory device 300 further includes a registering clockdriver (RCD) 310 that receives command/address signals from thecommand/address bus 306 and generates memory command/address signals forthe volatile memories 320. The RCD 310 can present a predictableelectrical load (e.g., for matching impedance, reactance, capacitance,etc.) to the host device and can re-drive memory command/address signalsto the volatile memories 320, which helps enable higher densities andincrease signal integrity. The RCD 310 may also buffer thecommand/address signals provided by the host, and then transmit thebuffered signals as memory command/address signals to the volatilememories 320.

The memory device 300 further includes a controller 332 for controllingthe non-volatile memory 330 and performing memory management operations,such as power loss detection, backup from the volatile memories 320 tothe non-volatile memory 330, and restore from the non-volatile memory330 to the volatile memories 320. The controller 332 may include aconnection to the edge connector 302 (not shown) to facilitate detectionof a power loss event (e.g., by monitoring a voltage of a power supplypin, or via a dedicated pin for sending commands from a connected hostto the controller 332).

The controller 332 can be a microcontroller, special purpose logiccircuitry (e.g., a field programmable gate array (FPGA), an applicationspecific integrated circuit (ASIC), etc.), or other suitable processor.The controller 332 can include a processor configured to executeinstructions stored in memory (e.g., embedded memory in the controller332 to store instructions for various processes, logic flows, androutines).

The controller 332 is connected to the non-volatile memory 330 by anon-volatile bus 334 and to the volatile memories 320 by the data bus304. In this regard, the data bus 304 may include a number of datamultiplexers 308 to facilitate connecting the volatile memories 320 toboth the edge connector 302 (e.g., for receiving data signals from andtransmitting data signals to a connected host) and to the controller 332(e.g., for reading data signals from the volatile memories 320 during abackup operation and transmitting data signals to the volatile memories320 during a restore operation). For example, in an embodiment in whicheach of nine DRAM memories 320 have eight I/O terminals, the data bus304 can include eight bus lines connecting each DRAM memory 320 to thecorresponding data multiplexer 308, eight bus lines connecting each datamultiplexer 308 to the edge connector 302, and eight bus linesconnecting each data multiplexer 308 to the controller 332 (e.g., whichcould be provided with 72 I/O terminals). In another embodiment, amemory module similar to NVDIMM 300 could include a further nine DRAMmemories 320 on a back side thereof (for 18 total DRAM memories 320,each having four I/O terminals). In such an embodiment, the data bus 304could include four bus lines connecting each of the eighteen DRAMmemories 320 to a corresponding one of eighteen data multiplexers 308,four bus lines connecting each data multiplexer 308 to the edgeconnector 302, and four bus lines connecting each data multiplexer 308to the controller 332 (e.g., which could be provided with 72 I/Oterminals).

The controller 332 is further connected to the volatile memories 320 sothat the controller 332 can provide memory command/address signals tothe volatile memories 320 during backup and restore operations. In thisregard, the controller can include a driver 333 for sending memorycommand/address signals to the volatile memories 320. Rather thanproviding command/address signals to the RCD 310, however, as in theNVDIMM illustrated in FIG. 2, the controller 332 of memory device 300 isconfigured to provide memory command/address signals to the volatilememories 320 through two memory command/address multiplexers 336, whichare configured to route memory command/address signals to the volatilememories 320 from both the driver 333 of controller 332 and the outputsof the RCD 310. Accordingly, the driver 333 of controller 332 may beconfigured to drive the memory command/address signals at one or morelevels specified by the design of the volatile memories 320 (e.g.,instead of at a level specified by the design of RCD 310).

Although in the embodiment illustrated in FIG. 3, controller 332 isshown as including a single driver 333 for providing command/addresssignals to all of the volatile memories 320 of the memory device 300, inother embodiments a controller can have multiple drivers. For example,FIG. 4 is a schematic diagram of a memory device in accordance with anembodiment of the present technology. The memory device 400 may be anNVDIMM, or have another alternative module format. The memory device 400includes a plurality of volatile memories 420 (e.g., DRAM memories) anda non-volatile memory 430 (e.g., NAND memory). The memory device 400includes an edge connector 402 for connecting a data bus 404 and acommand/address bus 406 (illustrated in bold lines) to a host device.The data bus 404 connects the volatile memories 420 to the edgeconnector 402 and receives data signals from and transmits data signalsto a connected host during memory access operations (e.g., reads andwrites). The memory device 400 further includes a registering clockdriver (RCD) 410 that receives command/address signals from thecommand/address bus 406 and generates memory command/address signals forthe volatile memories 420. The RCD 410 can present a predictableelectrical load (e.g., for matching impedance, reactance, capacitance,etc.) to the host device and can re-drive memory command/address signalsto the volatile memories 420, which helps enable higher densities andincrease signal integrity. The RCD 410 may also buffer thecommand/address signals provided by the host, and then transmit thebuffered signals as memory command/address signals to the volatilememories 420.

The memory device 400 further includes a controller 432 for controllingthe non-volatile memory 430 and performing memory management operations,such as power loss detection, backup from the volatile memories 420 tothe non-volatile memory 430, and restore from the non-volatile memory430 to the volatile memories 420. The controller 432 may include aconnection to the edge connector 402 (not shown) to facilitate detectionof a power loss event (e.g., by monitoring a voltage of a power supplypin, or via a dedicated pin for sending commands from a connected hostto the controller 432).

The controller 432 is connected to the non-volatile memory 430 by anon-volatile bus 434 and to the volatile memories 420 by the data bus404. For simplicity's sake, the memory device 400 of FIG. 4 isillustrated schematically with separate data buses coupling the volatilememories 420 to the edge connector 402 and to the controller 432 (e.g.,an embodiment in which each volatile memory 420 includes an internal DQmux, with four DQ nets coupled by the data bus 404 to the edge connector402, and four DQ nets coupled by the data bus 404 to the controller 432,switched via a mode register setting in the volatile memory 420), thoseof skill in the art will readily appreciate that different data busconfigurations can be used. The controller 432 is further connected tothe volatile memories 420 so that the controller 432 can provide memorycommand/address signals to the volatile memories 420 during backup andrestore operations. In this regard, the controller can include multipledrivers 433 a and 433 b for sending memory command/address signals tothe volatile memories 420. As compared to an embodiment with a singledriver, providing multiple drivers can improve the signal integrity ofthe command/address signals due to the reduced load per driver (albeitat a potentially higher cost and/or complexity). The controller 432 isconfigured to provide memory command/address signals to the volatilememories 420 through two memory command/address multiplexers 436, whichare configured to route memory command/address signals to the volatilememories 420 from both the corresponding driver 433 a or 433 b ofcontroller 432 and the outputs of the RCD 410. Accordingly, the drivers433 a and 433 b of controller 432 may be configured to drive the memorycommand/address signals at one or more levels specified by the design ofthe volatile memories 420 (e.g., instead of at a level specified by thedesign of RCD 410).

Although in the foregoing embodiments, memory devices having RCDs withmultiple outputs are shown, in other embodiments an RCD can have othernumbers of outputs. For example, FIG. 5 is a schematic diagram of amemory device in accordance with an embodiment of the presenttechnology, in which an RCD with a single output is provided. The memorydevice 500 may be an NVDIMM, or have another alternative module format.The memory device 500 includes a plurality of volatile memories 520(e.g., DRAM memories) and a non-volatile memory 530 (e.g., NAND memory).The memory device 500 includes an edge connector 502 for connecting adata bus 504 and a command/address bus 506 (illustrated in bold lines)to a host device. The data bus 504 connects the volatile memories 520 tothe edge connector 502 and receives data signals from and transmits datasignals to a connected host during memory access operations (e.g., readsand writes). The memory device 500 further includes a registering clockdriver (RCD) 510 that receives command/address signals from thecommand/address bus 506 and generates memory command/address signals forthe volatile memories 520. The RCD 510 can present a predictableelectrical load (e.g., for matching impedance, reactance, capacitance,etc.) to the host device and can re-drive memory command/address signalsto the volatile memories 520, which helps enable higher densities andincrease signal integrity. The RCD 510 may also buffer thecommand/address signals provided by the host, and then transmit thebuffered signals as memory command/address signals to the volatilememories 520.

The memory device 500 further includes a controller 532 for controllingthe non-volatile memory 530 and performing memory management operations,such as power loss detection, backup from the volatile memories 520 tothe non-volatile memory 530, and restore from the non-volatile memory530 to the volatile memories 520. The controller 532 may include aconnection to the edge connector 502 (not shown) to facilitate detectionof a power loss event (e.g., by monitoring a voltage of a power supplypin, or via a dedicated pin for sending commands from a connected hostto the controller 532).

The controller 532 is connected to the non-volatile memory 530 by anon-volatile bus 534 and to the volatile memories 520 by the data bus504. For simplicity's sake, the memory device 500 of FIG. 5 isillustrated schematically with separate data buses coupling the volatilememories 520 to the edge connector 502 and to the controller 532, thoseof skill in the art will readily appreciate that different data busconfigurations can be used. The controller 532 is further connected tothe volatile memories 520 so that the controller 532 can provide memorycommand/address signals to the volatile memories 520 during backup andrestore operations. In this regard, the controller can include a driver533 for sending memory command/address signals to the volatile memories520. The controller 532 is configured to provide memory command/addresssignals to the volatile memories 520 through a memory command/addressmultiplexer 536, which is configured to route memory command/addresssignals to the volatile memories 520 from both the driver 533 ofcontroller 532 and the outputs of the RCD 510. Accordingly, the driver533 of controller 532 may be configured to drive the memorycommand/address signals at one or more levels specified by the design ofthe volatile memories 520 (e.g., instead of at a level specified by thedesign of RCD 510).

Although in the foregoing embodiments, memory devices having a singlerank of volatile memories are shown, in other embodiments a memorydevice can have multiple ranks of memories. For example, FIG. 6 is aschematic diagram of a memory device having two ranks of memory inaccordance with an embodiment of the present technology. The memorydevice 600 may be an NVDIMM, or have another alternative module format.The memory device 600 includes a plurality of volatile memories 620(e.g., DRAM memories) arranged in two ranks 621 and 622, as well as anon-volatile memory 630 (e.g., NAND memory). The memory device 600includes an edge connector 602 for connecting a first data bus 604 and acommand/address bus 606 (illustrated in bold lines) to a host device.The edge connector 602 may include additional connections for separatelycontrolling the two ranks 621 and 622 of memory (e.g., via two chipselect terminals to provide a chip select signal to the memory device600 in order to enable the desired rank).

The first data bus 604 connects the volatile memories 620 to the edgeconnector 602 and receives data signals from and transmits data signalsto a connected host during memory access operations (e.g., reads andwrites). The memory device 600 further includes a registering clockdriver (RCD) 610 that receives command/address signals from thecommand/address bus 606 and generates memory command/address signals forthe volatile memories 620. The RCD 610 can present a predictableelectrical load (e.g., for matching impedance, reactance, capacitance,etc.) to the host device and can re-drive memory command/address signalsto the volatile memories 620, which helps enable higher densities andincrease signal integrity. The RCD 610 may also buffer thecommand/address signals provided by the host, and then transmit thebuffered signals as memory command/address signals to the volatilememories 620.

The memory device 600 further includes a controller 632 for controllingthe non-volatile memory 630 and performing memory management operations,such as power loss detection, backup from the volatile memories 620 tothe non-volatile memory 630, and restore from the non-volatile memory630 to the volatile memories 620. The controller 632 may include aconnection to the edge connector 602 (not shown) to facilitate detectionof a power loss event (e.g., by monitoring a voltage of a power supplypin, or via a dedicated pin for sending commands from a connected hostto the controller 632).

The controller 632 is connected to the non-volatile memory 630 by anon-volatile bus 634 and to the volatile memories 620 by a second databus 605. In this regard, although the memory device 600 of FIG. 6 isillustrated schematically with separate data buses coupling the volatilememories 620 to the edge connector 602 and to the controller 632 (e.g.,an embodiment in which each volatile memory 620 includes an internal DQmux, with first DQ nets coupled by the first data bus 604 to the edgeconnector 602, and second DQ nets coupled by the second data bus 605 tothe controller 632, switched via a mode register setting in the volatilememory 620), those of skill in the art will readily appreciate thatdifferent data bus configurations can be used. The controller 632 isfurther connected to the volatile memories 620 so that the controller632 can provide memory command/address signals to the volatile memories620 during backup and restore operations. In this regard, the controllercan include multiple drivers 633 a and 633 b for sending memorycommand/address signals to the volatile memories 620 (e.g., driver 633 asending memory command/address signals to rank 621 of the volatilememories 620 and driver 633 b sending memory command/address signals torank 622 of the volatile memories 620). The controller 632 is configuredto provide memory command/address signals to the volatile memories 620through four memory command/address multiplexers 636, which areconfigured to route memory command/address signals to the volatilememories 620 from both the drivers 633 a and 633 b of controller 632 andthe outputs of the RCD 610. Accordingly, the drivers 633 a and 633 b ofcontroller 632 may be configured to drive the memory command/addresssignals at one or more levels specified by the design of the volatilememories 620 (e.g., instead of at a level specified by the design of RCD610).

Although in the foregoing embodiments, memory devices having a singleRCD are shown, in other embodiments a memory device can have multipleRCDs. For example, FIG. 7 is a schematic diagram of a memory device inaccordance with an embodiment of the present technology. The memorydevice 700 may be an NVDIMM, or have another alternative module format.The memory device 700 includes a plurality of volatile memories 720(e.g., DRAM memories) arranged in two ranks 721 and 722, as well as anon-volatile memory 730 (e.g., NAND memory). The memory device 700includes an edge connector 702 for connecting a first data bus 704 and acommand/address bus 706 (illustrated in bold lines) to a host device.The edge connector 702 may include additional connections for separatelycontrolling the two ranks 721 and 722 of memory (e.g., via two chipselect terminals to provide a chip select signal to the memory device700 in order to enable the desired rank).

The first data bus 704 connects the volatile memories 720 to the edgeconnector 702 and receives data signals from and transmits data signalsto a connected host during memory access operations (e.g., reads andwrites). The memory device 700 further includes two registering clockdrivers (RCD) 710 that receive command/address signals from thecommand/address bus 706 and generate memory command/address signals forthe volatile memories 720. The RCDs 710 can present a predictableelectrical load (e.g., for matching impedance, reactance, capacitance,etc.) to the host device and can re-drive memory command/address signalsto the volatile memories 720, which helps enable higher densities andincrease signal integrity. The RCDs 710 may also buffer thecommand/address signals provided by the host, and then transmit thebuffered signals as memory command/address signals to the volatilememories 720.

The memory device 700 further includes a controller 732 for controllingthe non-volatile memory 730 and performing memory management operations,such as power loss detection, backup from the volatile memories 720 tothe non-volatile memory 730, and restore from the non-volatile memory730 to the volatile memories 720. The controller 732 may include aconnection to the edge connector 702 (not shown) to facilitate detectionof a power loss event (e.g., by monitoring a voltage of a power supplypin, or via a dedicated pin for sending commands from a connected hostto the controller 732).

The controller 732 is connected to the non-volatile memory 730 by anon-volatile bus 734 and to the volatile memories 720 by a second databus 705. In this regard, although the memory device 700 of FIG. 7 isillustrated schematically with separate data buses coupling the volatilememories 720 to the edge connector 702 and to the controller 732 (e.g.,an embodiment in which each volatile memory 720 includes an internal DQmux, with first DQ nets coupled by the first data bus 704 to the edgeconnector 702, and second DQ nets coupled by the second data bus 705 tothe controller 732, switched via a mode register setting in the volatilememory 720), those of skill in the art will readily appreciate thatdifferent data bus configurations can be used. The controller 732 isfurther connected to the volatile memories 720 so that the controller732 can provide memory command/address signals to the volatile memories720 during backup and restore operations. In this regard, the controllercan include multiple drivers 733 a and 733 b for sending memorycommand/address signals to the volatile memories 720 (e.g., driver 733 asending memory command/address signals to rank 721 of the volatilememories 720 and driver 733 b sending memory command/address signals torank 722 of the volatile memories 720). The controller 732 is configuredto provide memory command/address signals to the volatile memories 720through four memory command/address multiplexers 736, which areconfigured to route memory command/address signals to the volatilememories 720 from both the drivers 733 a and 733 b of controller 732 andthe outputs of the RCD 710. Accordingly, the drivers 733 a and 733 b ofcontroller 732 may be configured to drive the memory command/addresssignals at one or more levels specified by the design of the volatilememories 720 (e.g., instead of at a level specified by the design of RCD710).

Although in the foregoing exemplary embodiments, memory devices withDRAM-format volatile memory are illustrated, those of skill in the artwill readily appreciate that other volatile memory formats can beprovided on a memory device similarly configured. For example, a memorydevice using any one of, or any combination of, DRAM, SRAM, ZRAM,thyristor-RAM or the like could be provided in alternative embodimentsof the present technology.

Although in the foregoing exemplary embodiments, memory devices withNAND-format non-volatile memory are illustrated, those of skill in theart will readily appreciate that other non-volatile memory formats canbe provided on a memory device similarly configured. For example, amemory device using any one of, or any combination of, NAND, NOR, PCM,MRAM, FeRAM, ReRAM or the like could be provided in alternativeembodiments of the present technology.

FIG. 8 is a flow chart illustrating a method of operating a memorydevice in accordance with an embodiment of the present technology. Themethod includes receiving, at a connector of the memory device,command/address signals for a volatile memory of the memory device (box810). The method further includes providing the command/address signalsfrom the connector to a registering clock driver (RCD) of the memorydevice to generate memory command/address signals (box 820). The methodfurther includes providing the memory command/address signals from theRCD to a first input of a multiplexer (box 830). The multiplexer caninclude a second input connected to a non-volatile memory controller ofthe memory device. The method further includes providing the memorycommand/address signals from the multiplexer to the volatile memory ofthe memory device (box 840).

The method can further include detecting an event configured to triggera backup operation (box 850). The backup operation may include providingbackup command/address signals (e.g., including read commands for thevolatile memory) from the non-volatile memory controller to the secondinput of the multiplexer (box 860). In some embodiments, the controllermay first instruct the multiplexer to activate the second input of themultiplexer (e.g., and de-select the first input). The backup operationmay further include providing (box 870) the backup command/addresssignals from the multiplexer to the volatile memory (e.g., instructingthe volatile memory to read data from the volatile memory onto the databus). If the volatile memory includes multiple volatile memories, thebackup command/address signals may either be directed to the multiplevolatile memories serially, simultaneously, or some combination thereof(e.g., to more than one but less than all at a time, such as aright-side-first, left-side-second approach). If the volatile memoryincludes internal DQ muxes, the controller may include in the backupcommand/address signals an instruction to select the port(s) coupled bydata bus connections to the controller.

The method can further include a restore operation, which may includeproviding restore command/address signals (e.g., including writecommands for the volatile memory) from the non-volatile memorycontroller to the second input of the multiplexer (box 880). In someembodiments, the controller may first instruct the multiplexer toactivate the second input of the multiplexer (e.g., and de-select thefirst input). The restore operation may further include providing (box890) the restore command/address signals from the multiplexer to thevolatile memory (e.g., instructing the volatile memory to write datafrom the data bus to the volatile memory). If the volatile memoryincludes multiple volatile memories, the restore command/address signalsmay either be directed to the multiple volatile memories serially orsimultaneously, or some combination thereof (e.g., to more than one butless than all at a time, such as a right-side-first, left-side-secondapproach). If the volatile memory includes internal DQ muxes, thecontroller may include in the restore command/address signals aninstruction to select the port(s) coupled by data bus connections to thecontroller.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thescope of the invention. Accordingly, the invention is not limited exceptas by the appended claims.

What is claimed is:
 1. An apparatus, comprising: a first plurality ofvolatile memories; a second plurality of volatile memories; anon-volatile memory; a controller coupled to the non-volatile memory; aregistering clock driver (RCD) having a first RCD output and a secondRCD output; a first command/address (C/A) multiplexer including a firstC/A mux input coupled to the first RCD output, a second C/A mux inputcoupled to the controller, and a first C/A mux output coupled to thefirst plurality of volatile memories; and a second C/A multiplexerincluding a third C/A mux input coupled to the second RCD output, afourth C/A mux input coupled to the controller, and a second C/A muxoutput coupled to the second plurality of volatile memories.
 2. Theapparatus of claim 1, wherein the RCD has a RCD input coupled to anexternal connector of the apparatus by a command/address bus.
 3. Theapparatus of claim 1, wherein the controller includes a driverconfigured to generate command/address signals for the first and secondpluralities of volatile memories.
 4. The apparatus of claim 1, whereinthe first and second C/A multiplexers are configured to providecommand/address signals from either the RCD or the controller to thefirst and second pluralities of volatile memories, respectively.
 5. Theapparatus of claim 1, further comprising a backup power source.
 6. Theapparatus of claim 1, wherein the controller is configured to generatecommand/address signals to copy data from the first and/or secondpluralities of volatile memories to the non-volatile memory upondetecting a loss of power to the apparatus.
 7. The apparatus of claim 6,wherein the first and second C/A multiplexers are configured to ignorecommand/address signals from the RCD upon detecting the loss of power tothe apparatus.
 8. The apparatus of claim 6, wherein the controller isconfigured to generate command/address signals to copy data from thenon-volatile memory to the first and/or second pluralities of volatilememories upon recovery from the loss of power to the apparatus.
 9. Anapparatus, comprising: a first plurality of volatile memories; a secondplurality of volatile memories; a non-volatile memory; a controllercoupled to the non-volatile memory; a first registering clock driver(RCD); a second RCD; a first command/address (C/A) multiplexer includinga first C/A mux input coupled to an output of the first RCD, a secondC/A mux input coupled to the controller, and a first C/A mux outputcoupled to the first plurality of volatile memories; and a second C/Amultiplexer including a third C/A mux input coupled to an output of thesecond RCD, a fourth C/A mux input coupled to the controller, and asecond C/A mux output coupled to the second plurality of volatilememories.
 10. The apparatus of claim 9, wherein the first and secondRCDs each have an input coupled to an external connector of theapparatus by a command/address bus.
 11. The apparatus of claim 9,wherein the controller includes a driver configured to generatecommand/address signals for the first and second pluralities of volatilememories.
 12. The apparatus of claim 9, further comprising a backuppower source.
 13. The apparatus of claim 9, wherein the controller isconfigured to generate command/address signals to copy data from thefirst and/or second pluralities of volatile memories to the non-volatilememory upon detecting a loss of power to the apparatus.
 14. Theapparatus of claim 9, wherein the controller is configured to generatecommand/address signals to copy data from the non-volatile memory to thefirst and/or second pluralities of volatile memories upon recovery fromthe loss of power to the apparatus.
 15. An apparatus, comprising: asubstrate; a connector on the substrate, the connector configured toreceive first command/address signals; a controller on the substrate,the controller configured to generate second command/address signals; atleast one registering clock driver (RCD) on the substrate; a firstplurality of memories on the substrate; and a second plurality ofmemories on the substrate, wherein each of the first plurality ofmemories is configured to receive the first command/address signals fromthe connector through a first RCD output of the at least one RCD and toreceive the second command/address signals from the controller withoutintervening the at least one RCD therebetween, and wherein each of thesecond plurality of memories is configured to receive the firstcommand/address signals from the connector through a second RCD outputof the at least one RCD and to receive the second command/addresssignals from the controller without intervening the at least one RCDtherebetween.
 16. The apparatus of claim 15, wherein the controllerincludes a driver configured to generate the second command/addresssignals.
 17. The apparatus of claim 15, further comprising a backuppower source.
 18. The apparatus of claim 15, wherein the secondcommand/address signals are configured to copy data from the firstand/or second pluralities of memories to a third memory on the substrateupon detecting a loss of power to the apparatus.
 19. The apparatus ofclaim 18, wherein the controller is configured to generatecommand/address signals to copy data from the third memory to the firstand/or second pluralities of memories upon recovery from the loss ofpower to the apparatus.
 20. The apparatus of claim 15, wherein the atleast one RCD comprises a first RCD including the first RCD output and asecond RCD including the second RCD output.